Posiva in Finland and SKB in Sweden are preparing for spent nuclear fuel disposal in crystalline bedrock. Disposal relies on the geological KBS-3 multiple barrier concept. In this concept surrounding rock mass is considered as one barrier preventing radionuclide transportation to the biosphere. Excavation of disposal tunnels will be conducted using a drill and blast (D&B) tunneling method. Blasting and stress field redistribution unavoidably causes an excavation damaged zone (EDZ) which needed to be investigated. This study concentrates on characterization methods revealing the properties and significance of the EDZ. Non-destructive testing (NDT) methods were advised to enhance coverage and efficiency of investigations. Chosen study methods were seismic reflection and tomography, electrical resistivity tomography, ground penetrating radar investigations, borehole imaging, hydraulic measurements and laboratory analysis of rock samples. Results obtained from different scales and the chosen methods were compared. Analysis led to observation of discontinuous character and varying thickness of the EDZ. Research indicates a fairly thin, 5-30 cm thick EDZ layer on rock surfaces. Excavation and stress redistribution induced fractures might contribute to hydraulic flow close to the tunnel perimeter. Locating and mapping of these potential hydraulic paths can be performed with high resolution geophysical NDT methods. Copyright 2013 ARMA, American Rock Mechanics Association.
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